fix #347: Make Target::setCostumeIndex() virtual

Author: adazem009

include/scratchcpp/sprite.h

@@ -50,7 +50,7 @@ class LIBSCRATCHCPP_EXPORT Sprite : public Target
         double size() const;
         void setSize(double newSize);
 
-        void setCostumeIndex(int newCostumeIndex);
+        void setCostumeIndex(int newCostumeIndex) override;
 
         double direction() const;
         void setDirection(double newDirection);

include/scratchcpp/stage.h

@@ -30,7 +30,7 @@ class LIBSCRATCHCPP_EXPORT Stage : public Target
 
         bool isStage() const override;
 
-        void setCostumeIndex(int newCostumeIndex);
+        void setCostumeIndex(int newCostumeIndex) override;
 
         int tempo() const;
         void setTempo(int newTempo);

include/scratchcpp/target.h

@@ -57,7 +57,7 @@ class LIBSCRATCHCPP_EXPORT Target
         int findComment(const std::string &id) const;
 
         int costumeIndex() const;
-        void setCostumeIndex(int newCostumeIndex);
+        virtual void setCostumeIndex(int newCostumeIndex);
 
         std::shared_ptr<Costume> currentCostume() const;